urbaf2

AROMATIC NITRO COMPOUNDS 209

The nature of the Janovsky’s colour reaction is not sufficiently understood.

Reitzenstein and Stamm [55] were the first to try to establish the structure of the

compounds formed. They were able to isolate from an acetone solution a brown

product (IV), resulting from the reaction of 1,2,4-chlorodinitrobenzene with the

enolic form of acetone:

IV

Quite recently Gitis [42] isolated a number of coloured products formed by

polynitro compounds with acetone in the presence of sodium hydroxide. The author,

like Reitzenstein and Stamm, postulated that it was the enol form of acetone that

reacted with a nitro compound, products of nucleophilic substitution of the type

described by Meisenheimer [36-38] (p. 202), being formed:

V

(29)

Gitis believes that compounds of the V type are the main products of the Janovsky

reaction.

The formula V is not in agreement with the views expressed by various authors

on the structure of the coloured products obtained by adding substances containing

an active methylene group to higher nitrated aromatic compounds, starting from

m- dinitrobenzene. A number of papers have been published on the subject. They ori -

ginated from the Jaffe-Folin [63,64] reaction for quantitative calorimetric determi-

nation of creatinine. The reaction consists in the development of a red colour

when solutions containing creatinine are treated with aqueous picric acid and a

few drops of alkali at room temperature. Many (but not all) compounds with

active CH 2 group are capable of giving this reaction.

Several red compounds have been isolated from the red solution obtained

from creatinine, picric acid and alkali. By acidification a red powder was isolated

by Greenwald and Gross [65]. On boiling with water (Anslow and King [66]) or

on heating to 139°C this was transformed into the usual yellow creatinine picrate.